tell my why this thing should not be able to melt satelites that cross over during the day
My scientific research of squinting at the poster says a spy satellite is probably about as long as a pickup truck which is probably about 20 feet long.
xkcd says space is 100 km away and I'm sure there's nothing else I need to understand about that.
At 100 km away, the change of angle that will move your beam by 20 feet (enough to make the difference between hitting or not, if the thing and the flat mirror are both about 20 feet long I guess) is (20 feet / 100 km / pi) radians or 0.0000194 radians, meaning you raised or lowered one edge of the mirror by 0.004 inches or around the width of pretty-thick hair. I would be a little surprised if the mirrors even stayed within that tolerance just from flexing around in the wind for as big as they are.
On the other hand, you wouldn't have to hit the spy satellite with every mirror; you could probably heat it up significantly just by hitting it with a bunch of the beams as they were swinging wildly around and mostly missing it. And if it was specifically a spy satellite, you could probably fry its optics with not really a lot of mirrors for not a long time actually managing to hit it.
On the other other hand the thing would be flying along at around 8 km/s, so you'd have to get your mirrors positioned accurately enough, and then start moving them at a relatively insane speed while still keeping their absolute positioning dead accurate when their motors and overall construction clearly weren't designed for either of those tasks at the required level of precision.
TL;DR Let's try it
and then start moving them at a relatively insane speed while still keeping their absolute positioning dead accurate when their motors and overall construction clearly weren't designed for either of those tasks at the required level of precision.
That's what they want you to think.
Props on your Internet math and research. It was a fun read.
You still have a crap-ton of atmosphere you have to get through, and the beams being reflected aren't coherent. So the light reflected is subject to the inverse square law, which means that the energy diminishes as the inverse square of the distance. So the actually energy reaching the satellite would be minuscule. If you want to effectively use light to punch all the way through the atmosphere, you'll need beam coherence.
I realize we've had disagreements in other regards but this is excellent
I think solar-powered lasers would be a better bet. That would eliminate any surface irregularities of the mirrors and reduce the effective focus area . This would also reduce the number of moving parts required for focusing.
On the other hand, the amount of particulate diffusion within the atmosphere would complicate both the accuracy of the beam and the effective beam area, so who knows.
Let's try it.
The fucking watermelon killed me
Also, great write up honestly I loved it lol
The mirrors are flat, and the sun has an apparent diameter of about half a degree, so at 100 km, the spot diameter would be 900 meters.
You could use concave mirrors, but since you're moving them independently, you'd also have to consider the diffraction limit for each one.
The suns angular diameter is about 0.01 radian, so at a distance of 100km, the suns reflection will spread out to a disc about 1km across.
392MW over a disc that size is 500w/m2, which is weaker than direct sunlight.
Uh… losses from transmitting through the atmosphere a second time?
Damn. I wonder what its operational range would be.
Because it's always nighttime in space.
I suspect in order to stay focused on such distances you'd need extremely flat mirrors. Like, telescope grade stuff.
I doubt the mirrors they have is even within an order of magnitude flat enough.
You might even need adaptive mirrors to deal with atmospheric distortion. Also, they would have to move relatively quickly and very precisely (read: an impossible combination) to track satellites in low orbit. Plus, you could only hit satellites that crossed overhead at a relatively high angle.
But yeah, one solar tower plant did a stunt where they reflected an image made of sunlight at the ISS and an astronaut took a picture. They didn't melt.
I'm no optical physicist, but based on empirical evidence of not melting due to light arriving from a huge ball of thermonuclear fire 8 light minutes away (and sure it's not exactly focused), I propose a hypotesis that light-based energy transfer in atmosphere is very lossy and not feasible as a weapon.
Which is perfect for this community, of course.
You damn scientists and your sciencing.
Those are designed to focus on a large, stationary, object not far away, not a small hypersonic object very very far away.
thats what they want you to think
If its a optical image satellite, it probably doesnt take much to burn on the camera if it's shutter is open.
Someone's been drinking their government supplied fluoride tainted tap water, you're thinking like one of them. Don't believe The Man's lies!
… for now!
Satellites be zoomin, it would be hard to hit one for more than a split second. But I'm definitely down to try!
Because of how far it is I'm guessing they could move the focal point very fast too with just the slightest of movements in the mirrors.
I imagine the precision needed for that is lacking in a solar mirror motor.
Small satellite that's at least 100km away
Who do you think you are? Archimedes?
Isn’t there some inverse square math rule about radiation like this? The further away you are the radiation reaching you is far less than it would seem? Not good at remembering this math so maybe someone can correct me.
Even if you could get the mirrors all focused accurately and tracking the object at speed it seems like it wouldn’t be any more of a concern than a really bright searchlight or something.
The power density square law is for an emitting light source that emits in all directions. Since the incoming light is basically parallel that doesn't really apply. If you were able to accurately track a satellite (a feat I'm sure is pretty hard) you would definitely vaporize it pretty quickly I'm talking under a minute since space is a good insulator.
It holds if the light spreads wider than the target. So also for directed light sources at large enough distances. Even a perfect mirror must spread the light in the same angle as it is incomming. Hence the beam would at least 3 km wide at the satellite. Therefore the satellite can only recieve a Illumination of ~65W/m^2 which is a few percent of the normal sun brightness of 1300 W/m^2.
Another way to look at it, the mirrors cant make the sun seem brighter only larger. From the tower you see a large solid angle around you the mirror, therefore, it can seem like you are at the surface of the sun. However, fro. the position of a satellite, the power plant only takes a small solid angle, so it seems like a "smaller" sun. Assuming 400 MW and 1 kW/m^2 (at surface) solar power, it has an area of 400000 m^2, so a solid angle of 4.5e-6 sr from 300km while the sun has 70e-6 sr. So ten times smaller, therefore weaker. Note however here i did not account for attenuation in the atmosphere
Thank you.
There is a cool easy-to-show fact that you can never make something hotter than the light source my focusing its light.
Since otherwise you could take heat and divide it into a hotter and colder region, decreasing entropy without using energy.I'm not sure about the easy-to-show part, but take a look at the Brightness Theorem / Conservation of https://en.wikipedia.org/wiki/Etendue if you want to learn more.
They would have to adjust really quickly to track
But really tiny adjustments, because it's far away.
Also there's a spread in the beam, so that's nice.
Also, as I pointed out elsewhere here, there's a vacuum-bottle effect. You can just pump heat into it. And also you don't need to melt it, just overheat the electronics.
The movement would need to be incredibly precise.
Yeah except the focal point of those mirrors is measured in meters not 100s of kilometers. You can't use them to focus on something that far away.
All this science talk but the first thing I thought of was a reference to Fallout New Vegas.
I love the fact that those towers are so bright they glitch up Google maps satellite view.
Seeing them at a distance while driving from Primm to Nipton was fucking intense, that shit is overwhelmingly bright.
Would it be safe to live somewhere nearby?
Unsure if there were any residencies near it. There's a pretty good distance from the road to the closest of the towers. I do believe there is a golf course not far from it.
... In the middle of THE driest region in the country.
Patrolling the Mojave wasteland almost makes you wish for a nuclear winter.
Thank you it was in my head
Satellite is surrounded by vacuum. Thus insulated from getting rid of heat that way. So just pump heat into it and watch the temperature rise.
And you don't need to melt it. Just cook it till its electronics overheat.
I disagree, you need to melt it, because space is more interesting when its full of lances of molten metal whipping about at orbital speeds
Well all things (human) in space have special paint in order to modify their blackbody radiation and maintain a trade off between disipation heat by EM radiation and keeping a temperature that allows semiconductors to work.
The point is that satellites do disipate heat. Convection disipation is the worst disipation of heat. The best disipation of energy (heat) is by radiation. Thats why the thermal blankets look shinny weird, just like the satellites. You would need a realiable source of heat in order to overcome the satellite disipation and saturate the satellite.
i've never thought about that before.
isnt that untrue though given that objects freeze instantly in space? Also that would mean you would only need to heat the ISS (rip) once, during its conception.
What mariusafa said is correct, but I wanted to point out that objects in space do not freeze immediately. Dissipation via blackbody radiation is much slower than convection and it can take a long time for something to cool down without the latter. In other words, a vaccuum does function as a very effective insulator, which can sometimes make it more challenging to get rid of heat in space than it is to keep something warm. The ISS, for example, needs to use radiators to keep cool. The same goes for many (most? all?) satellites that are at least as close to the sun as the earth.
It's just not true. Disipation by convection effect is one of the ways of disipating energy. Dissipation by blackbody radiation is where most of the energy goes.
For example infrared heaters transmits most of it's heat by radiation. Efficient heaters do not use convection mechanisms, well or not only.
Euclid C Finder go brrrrrr 💥
There is the matter of space debris, which is already a problem. If you're going to attack satellites to disable them you want to capture them in a decaying orbit.
pfff just use the massive amounts of photones to push it into a higher graveyard orbit
Or, hear me out, nukes. Explode a nuke far away enough that the shockwave doesn't matter (not like it matters much in space anyway) and use the EMP to knock the satellite out.
Nukes solve a lot of problems.
All low earth orbits are decaying without periodic adjustments. If you disable a satellite, it will eventually burn up in the atmosphere.
Some orbits are quicker than others. Cloudsat was recently retired, and was lowered to a graveyard orbit which decays a lot more quickly. As I understand it, our collective space programs have made a bit of a mess of operational orbits and we need to think about cleaning up debris while also mitigating any future additions to the debris field.
My brain has been poisoned too thoroughly by New Vegas for me to make any vaguely reasonable comment. W should make Archimedes and melt putin into a puddle.
I don't do this often but this
*Jesse, what the hell are you talking about?
With one ?, he's not scared or anything.
